Treatment of atrial fibrillation by overlapping curvilinear lesions

ABSTRACT

Ablation methods and instruments are disclosed for creating lesions in tissue, especially cardiac tissue for treatment of arrhythmias and the like. Percutaneous ablation instruments in the form of coaxial catheter bodies are disclosed having at least one central lumen therein and having one or more balloon structures at the distal end region of the instrument. The instruments include an energy emitting element which is independently positionable within the lumen of the instrument and adapted to project radiant energy through a transmissive region of a projection balloon to a target tissue site to form a series of lesions on the target tissue.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.10/357,156, filed on Feb. 3, 2003, now U.S. Pat. No. 8,025,661, which isa continuation-in-part of U.S. patent application Ser. No. 09/924,394,filed on Aug. 7, 2001, now U.S. Pat. No. 6,579,285 issued Jun. 17, 2003,which is a continuation-in-part of U.S. patent application Ser. No.09/390,964, filed on Sep. 7, 1999, now U.S. Pat. No. 6,270,492 issuedAug. 7, 2001, which is a continuation-in-part of U.S. patent applicationSer. No. 08/991,130, filed on Dec. 16, 1997, now U.S. Pat. No. 5,947,959issued Sep. 7, 1999, which is a continuation-in-part of U.S. patentapplication Ser. No. 08/827,631, filed on Apr. 10, 1997, now U.S. Pat.No. 5,908,415 issued Jun. 1, 1999, which is a continuation of U.S.patent application Ser. No. 08/303,605, filed on Sep. 9, 1994, nowabandoned.

Additionally, U.S. patent application Ser. No. 10/357,156 is acontinuation-in-part of U.S. patent application Ser. No. 09/616,275,filed on Jul. 14, 2000, now U.S. Pat. No. 6,626,900 issued Sep. 30,2003, which is a continuation-in-part of U.S. patent application Ser.No. 09/602,420 filed on Jun. 23, 2000, now U.S. Pat. No. 6,572,609issued Jun. 3, 2003, which is a continuation-in-part of U.S. patentapplication Ser. No. 09/357,355, filed on Jul. 14, 1999, now U.S. Pat.No. 6,423,055 issued Jul. 23, 2002.

The teachings of all of these prior related applications are herebyexpressly incorporated by reference.

BACKGROUND OF THE INVENTION

The present invention relates to ablation instruments for the ablationof tissue for the treatment of diseases, and, in particular, topercutaneous instruments employing radiant energy. Methods of ablatingtissue using radiant energy are also disclosed. The instruments can beused, for example, in the treatment of cardiac conditions such ascardiac arrhythmias.

Cardiac arrhythmias, e.g., fibrillation, are irregularities in thenormal beating pattern of the heart and can originate in either theatria or the ventricles. For example, atrial fibrillation is a form ofarrhythmia characterized by rapid randomized contractions of atrialmyocardium, causing an irregular, often rapid ventricular rate. Theregular pumping function of the atria is replaced by a disorganized,ineffective quivering as a result of chaotic conduction of electricalsignals through the upper chambers of the heart. Atrial fibrillation isoften associated with other forms of cardiovascular disease, includingcongestive heart failure, rheumatic heart disease, coronary arterydisease, left ventricular hypertrophy, cardiomyopathy, or hypertension.

Various techniques have been proposed for the treatment of arrhythmia.Although these procedures were originally performed with a scalpel,various other techniques have also been developed to form lesions.Collectively, these treatments are referred to as “ablation.” Innon-surgical ablations, the tissue is treated, generally with heat orcold, to cause coagulation and/or tissue necrosis (i.e., celldestruction). In each of these techniques, cardiac muscle cells arereplaced with scar tissue which cannot conduct normal electricalactivity within the heart.

For example, the pulmonary vein has been identified as one of theorigins of errant electrical signals responsible for triggering atrialfibrillation. In one known approach, circumferential ablation of tissuewithin the pulmonary veins or at the ostia of such veins has beenpracticed to treat atrial fibrillation. Similarly, ablation of theregion surrounding the pulmonary veins as a group has also beenproposed. By ablating the heart tissue (typically in the form of linearor curved lesions) at selected locations, electrical conductivity fromone segment to another can be blocked and the resulting segments becometoo small to sustain the fibrillatory process on their own.

Several types of ablation devices have recently been proposed forcreating lesions to treat cardiac arrhythmias, including devices whichemploy electrical current (e.g., radio-frequency “RF”) heating orcryogenic cooling. Such ablation devices have been proposed to createelongated lesions that extend through a sufficient thickness of themyocardium to block electrical conduction. Many of the recently proposedablation instruments are percutaneous devices that are designed tocreate such lesions from within the heart. Such devices are positionedin the heart by catheterization of the patient, e.g., by passing theablation instrument into the heart via a blood vessel, such as thefemoral vein.

Devices that rely upon resistive or conductive heat transfer can beprone to serious post-operative complications. In order to quicklyperform an ablation with such “contact” devices, a significant amount ofenergy must be applied directly to the target tissue site. In order toachieve transmural penetration, the surface that is contacted willexperience a greater degree of heating (or freezing). For example, in RFheating of the heart wall, a transmural lesion requires that the tissuetemperature be raised to about 50° C. throughout the thickness of thewall. To achieve this, the temperature at the contact surface willtypically be raised to greater than 100° C. In this temperature regime,there is a substantial risk of tissue destruction (e.g., due to watervaporization micro-explosions or due to carbonization). Charring of thesurface of the heart tissue, in particular, can lead to the creation ofblood clots on the surface and post-operative complications, includingstroke. Even if structural damage is avoided, the extent of the lesion(i.e., the width of the ablated zone) on the surface that has beencontacted will typically be greater than necessary.

Ablation devices that do not require direct contact have also beenproposed, including acoustic and radiant energy. Acoustic energy (e.g.,ultrasound) is poorly transmitted into tissue (unless a coupling fluidis interposed). Laser energy has also been proposed but only in thecontext of devices that focus light into a scalpel-like point or similarhigh intensity spot pattern. When the light energy is delivered in theform of a focused spot, the process is inherently time consuming becauseof the need to expose numerous spots to form a continuous linear orcurved lesion.

In addition, existing instruments for cardiac ablation also suffer froma variety of design limitations. The shape of the heart muscle adds tothe difficulty in accessing cardiac structures, such as the pulmonaryveins on the anterior surface of the heart. Typically, percutaneousdevices are positioned with the assistance of a guide wire, which isfirst advanced into heart. In one common approach, described, forexample, in U.S. Pat. No. 6,012,457 issued to Lesh on Jan. 11, 2000 andin International Application Pub. No. WO 00/67656 assigned to Atrionix,Inc., a guide wire or similar guide device is advanced through the leftatrium of the heart and into a pulmonary vein. A catheter instrumentwith an expandable element is then advanced over the guide and into thepulmonary vein where the expandable element (e.g., a balloon) isinflated. The balloon structure also includes a circumferential ablationelement, e.g., an RF electrode carried on the outer surface of theballoon, which performs the ablation procedure. The balloon must belarge enough and sufficiently rigid to hold the electrode in contactwith the inner surface of the pulmonary vein for the length of theprocedure. Moreover, because the lesion is formed by an ablation elementcarried on the surface of the balloon element, the balloon shapeinherently limits the locations where a lesion can be formed, i.e., thelesion must be formed at least partially within the pulmonary vein.

In another approach described in U.S. Pat. No. 6,235,025 issued toSwartz et al. on May 22, 2001, a guide wire is again used topercutaneously access a pulmonary vein and a catheter is again slid overthe guide to a position within the pulmonary vein. The catheter deviceincludes two spaced-apart balloons, which are inflated in the vein (orin the vein and at its mouth). The space between the two balloons canthen be filled with a conductive fluid to delivery RF energy (or,alternatively, ultrasound) to the vein and thereby induce a conductionblock in the blood vessel by tissue ablation. With the Swartz et al.device, like the Lesh device, the region where tissue ablation can occuris limited by the design. Because two balloons must seal a space that isthen filled with an ablative fluid, the lesion is necessarily formedwithin the pulmonary vein.

Ablation within the pulmonary vein can result in complications.Overtreatment deep within a vein can result in stenosis (closure of thevein itself), necrosis or other structural damage, any of which cannecessitate immediate open chest surgery.

A major limitation in the prior art percutaneous designs is the lack ofsite selectability. Practically speaking, each prior art percutaneousinstrument is inherently limited by its design to forming an ablativelesion at one and only one location. For example, when an expandableballoon carrying an RF heating device on its surface is deployed at themouth of a vein, the lesion can only be formed at a location defined bythe geometry of the device. It is not possible to form the lesion atanother location because the heating element must contact the targettissue. Similarly, the above-described tandem balloon device can onlyform a lesion at a location defined by the space between the balloonsthat is filled with the ablative fluid.

Another major limitation in prior art percutaneous designs is theirinability to accommodate the actual and quite varied geometry of theheart. The inner surface of the atrium is not regular. In particular,the mouths of the pulmonary veins do not exhibit regularity; they oftenbear little resemblance to conical or funnel-shaped openings. When theexpandable, contact heating devices of the prior art encounterirregularly-shaped ostia, the result can be an incompletely formed(non-circumferential) lesion.

Accordingly, a percutaneous ablation device that allows the clinician toselect the location of the ablation site would be highly desirable. Aninstrument that allows a clinician to choose from a number of differentlesion locations, especially in creating continuous conduction blocksaround pulmonary veins, would satisfy a long felt need in the art.

Moreover, the prior art devices typically can not determine whethercontinuous circumferential contact has been achieved before heatingcommences. These devices most often rely on post-ablation electricalmapping to determine whether a circumferential lesion has been formed.If electrical conduction is still present, the encircling lesion isincomplete and the procedure must be repeated or abandoned.

Accordingly, there also exists a need for better surgical ablationinstruments that can form lesions with less trauma to the healthy tissueof the heart and greater likelihood of success. A percutaneous systemthat could determine whether contact has been achieved (or blood hasbeen cleared from the target site) and predict success based on suchdeterminations would represent a significant improvement over theexisting designs.

SUMMARY OF THE INVENTION

Ablation methods and instruments are disclosed for creating lesions intissue, especially cardiac tissue, for treatment of arrhythmias and thelike. In one aspect of the invention, percutaneous ablation instrumentsin the form of coaxial catheter bodies are disclosed having at least onecentral lumen therein and having one or more balloon structures at thedistal end region of the instrument. The balloon structure and catheterbodies are at least partially transmissive to ablative energy. Theinstruments can further include an energy emitting element, which isindependently positionable within the lumen of the instrument andadapted to project ablative energy through a transmissive region of theballoon to a target tissue site. The energy is delivered without theneed for contact between the energy emitter and the target tissuebecause the methods and devices of the present invention do not relyupon conductive or resistive heating. Because the position of theradiant energy emitter can be varied, the clinician can select thelocation of the desired lesion.

In another aspect of the invention, a cardiac ablation instrument isdisclosed having a catheter body adapted for disposition within a heart,and a projection balloon connected to the catheter body and adapted forinflation within the heart to provide a transmission pathway forablative energy to be delivered to a target tissue site. The cardiacablation instrument also includes an energy emitter disposable withinthe balloon at a plurality of locations for the projection of ablativeenergy through the balloon to form a series of lesions. The energyemitter can be positionable at a plurality of locations along alongitudinal axis within the balloon or it can be adapted fortranslatory motion to a plurality of locations within the balloon. Inone embodiment, the energy emitter is adapted to be positioned at alocation where a pulmonary vein extends from an atrium and the series oflesions can encircle an ostium of the pulmonary vein. The energy emittercan project at least a partial ring of radiant ablative energy ofvariable diameter based on its axial position within the catheter body.

The energy emitter can be adapted to deliver a variety of types ofenergy. In one embodiment, the energy emitter can be a radiant energyemitter that optionally can include a light transmitting optical fiberthat is adapted to receive radiant energy from a light source and alight emitting tip at a distal end of the fiber for emitting light. Thelight emitting tip can further include a beam forming optical waveguidefor projecting an annular beam of light, such that the radiant energyemitter projects a ring of ablative energy of variable diameter based onits axial position within the catheter body, or alternatively, a lightdiffusing element.

In another embodiment, the energy emitter can include an ultrasoundgenerator, and can generate ultrasound energy at at least one wavelengthin the range of about 5 MHz to 20 MHz. Alternatively, the energy emittercan include a microwave generator, a contact heating element located ata distal end of the catheter body, at least one electrode adapted tocouple to an electric current source, such as a radiofrequency currentsource, or a cryogenic ablation element.

The instrument can also have a variety of other features, and canfurther include a contact sensor, a detector capable of distinguishingat least two wavelengths of reflected light, a light source forgenerating photoablative radiation at wavelengths in the range of about800 nm and 1000 nm, and/or a second catheter body with an inner channelconfigured for coupling to the first catheter body via the channel suchthat the second catheter body can be passed over the first catheter bodyinto a position within the heart, and/or an inflatable projectionballoon which can be deployed to clear blood from a surrounding regionwithin the heart. The catheter body can also be adapted for dispositionover a guide wire.

Methods of treating atrial fibrillation are also disclosed herein. Inone aspect, the method can include positioning a cardiac ablationinstrument in proximity to a target region of a heart, the instrumenthaving a catheter body with at least one lumen therein and an energyemitting element independently positionable within the at least onelumen of the catheter body, and activating the energy emitting elementto project ablative energy to form a first lesion in proximity to thetarget region. The method can further include activating the energyemitting element to project ablative energy to form at least a secondlesion in proximity to the target region, the at least second lesionoverlapping a portion of the first lesion so as to form a combinedlesion that continuously encircles the target region. The energyemitting element can be positioned at a different location afteractivating the energy emitting element to form the first lesion. In oneembodiment, the target region is a pulnonary vein, and the combinedlesion circumscribes the pulmonary vein.

The lesions formed can have a variety of configurations, and each lesioncan be partially circumferential, in the shape of an arc, or have asimilar thickness. Additionally, the position of the energy emittingelement can be adjusted to form a lesion having a different thicknessthan a previous lesion.

The method can also include inflating a projection balloon to clearblood from a transmission pathway between the energy emitting elementand a target region of the cardiac tissue. In one embodiment, whether aclear transmission path exists between the energy emitting element andthe target region can be determined is based on reflectance measurementsby an optical sensor disposed within the ablation instrument by, forexample, measuring at least two different wavelengths of reflected lightcollected by the optical sensor to determine whether a projection pathhas been established.

A variety of energy emitting elements can be activated to form a lesionon tissue. In one embodiment, activating the energy emitting element caninclude activating a beam-forming optical waveguide to expose the targetregion to an annular beam of light energy to induce the combined lesionin cardiac tissue or, alternatively, activating an ultrasound emittingelement to expose the target region to acoustic energy to inducephotocoagulation of cardiac tissue within the target region. In otherembodiments, activating the energy emitting element can includeactivating a light emitting element to expose the target region to lightenergy to induce photocoagulation of cardiac tissue within the targetregion, activating a light emitting element to expose the target regionto light energy to induce the combined lesion in the cardiac tissue,activating an ultrasound emitting element to expose the target region toacoustic energy to induce photocoagulation of cardiac tissue within thetarget region, or activating a radiation emitting element to expose thetarget region to at least one form of radiant energy selected from thegroup consisting of microwave, x-ray, gamma-ray and ionizing radiationto induce photocoagulation of cardiac tissue within the target region.By way of non-limiting example, photoablative radiation can be generatedat a wavelength in the range of about 800 nm to 1000 nm, and morepreferably from about 915 nm to 980 nm.

In another aspect of the invention, generally applicable to a wide rangeof cardiac ablation instruments, mechanisms are disclosed fordetermining whether the instrument has been properly seated within theheart, e.g., whether the device is in contact with a pulmonary veinand/or the atrial surface, in order to form a lesion by heating, coolingor projecting energy. This contact-sensing feature can be implemented byan illumination source situated within the instrument and an opticaldetector that monitors the level of reflected light. Measurements of thereflected light (or wavelengths of the reflected light) can thus be usedto determine whether contact has been achieved and whether such contactis continuous over a desired ablation path.

The instruments are especially useful in percutaneous access cardiacsurgery for rapid and efficient creation of curvilinear lesions to serveas conduction blocks. The instruments are designed to create lesions inthe atrial tissue in order to electrically decouple tissue segments onopposite sides of the lesion while presenting low profiles duringpercutaneous access and retraction. The instruments of the presentinvention permit the formation of continuous lesions in the atrial walltissue of the heart, such that the continuous lesion can surround aorgan structure, such as a pulmonary vein, without involving thestructure itself.

In one embodiment, a cardiac ablation instrument is disclosed having acatheter body adapted for disposition within a heart. This catheter bodyhas at least one lumen therein and an expandable, energy-transmittingelement which can be deployed at the desired location with or without ananchorage element to contact a cardiac structure and establish atransmission pathway. For example, the expandable element can be aprojection balloon that is expandable to fill the space between theenergy emitter and the target tissue with an energy-transmissive fluidand, thereby, provide a transmission pathway for projected radiantenergy. The instrument further includes a radiant energy deliveryelement movable within the lumen of the catheter body such that it canbe disposed at the desired location and deliver radiant energy through atransmissive region of the instrument to a target tissue site. Theinstrument can further include additional elements, such as fluiddelivery ports, to provide a blood-free transmission pathway from theenergy emitter to the target tissue.

In another embodiment, a cardiac ablation instrument is disclosed havinga catheter body adapted for disposition within a heart and at least oneanchorage element which can be deployed at a desired location to contacta cardiac structure and secure the device in place. The instrument againincludes a radiant energy delivery element movable within the lumen ofthe catheter body such that it can be disposed at the desired locationand deliver radiant energy through a transmissive region of theinstrument to a target tissue site. A projection balloon can again beemployed, alone or together with fluid releasing mechanisms, to providea blood-free transmission pathway from the energy emitter to the tissuetarget.

Mechanisms are disclosed for determining whether the ablationinstruments of the present invention have been properly seated withinthe heart to form a lesion. For example, if a projection balloon isemployed to provide a clear transmission pathway from a radiant energyemitter to the target tissue, the mechanisms of the present inventioncan sense whether contact has been achieved between the balloon and thetarget tissue (and/or whether the pathway for projection of radiantenergy has been otherwise cleared of obstructions). In one embodiment,this contact-sensing feature can be implemented by an illumination fibersituated within the instrument and an optical detector fiber (or fiberassembly) that monitors the level of reflected light. Measurements ofthe reflected light (or wavelengths of the reflected light) can thus beused to determine whether contact has been achieved between theprojection balloon and the target tissue, whether blood has been clearedfrom any gaps, and whether a clear and continuous transmission pathwayhas been established over a desired ablation path.

In a further aspect of the invention, percutaneous instruments aredisclosed that can achieve rapid and effective photoablation through theuse of tissue-penetrating radiant energy. It has been discovered thatradiant energy, e.g., projected electromagnetic radiation or ultrasound,can create lesions in less time and with less risk of the adverse typesof surface tissue destruction commonly associated with prior artapproaches. Unlike instruments that rely on thermal conduction orresistive heating, controlled penetrating radiant energy can be used tosimultaneously deposit energy throughout the full thickness of a targettissue, such as a heart wall, even when the heart is filled with blood.Radiant energy can also produce better defined and more uniform lesions.

The use of radiant energy, in conjunction with catheter structures thatare substantially transparent to such radiation at the therapeuticwavelengths, is particularly advantageous in affording greater freedomin selecting the location of the lesion, e.g., the site is no longerlimited to the pulmonary vein itself. Because the energy can beprojected onto the tissue, a ring-like lesion can be formed in atrialtissue at a distance from the vein, thereby reducing the potential forstenosis and/or other damage to the vein itself.

It has also been discovered that infrared radiation is particularlyuseful in forming photoablative lesions. In certain preferredembodiments, the instruments emit radiation at a wavelength in a rangefrom about 800 nm to 1000 nm, and preferably at a wavelength in a rangeof about 915 nm to 980 nm. Radiation at a wavelength of about 915 nm orabout 980 nm is commonly preferred, in some applications, because of theoptimal absorption of infrared radiation by cardiac tissue at thesewavelengths.

In another embodiment, focused ultrasound energy can be used to ablatecardiac tissue. In certain preferred embodiments, an ultrasoundtransducer can be employed to transmit frequencies within the range ofabout 5 MHz to 20 MHz, and preferably in some applications within therange of about 7 MHz to 10 MHz. In addition, the ultrasonic emitter caninclude focusing elements to shape the emitted energy into an annularbeam.

However, in certain applications, other forms of radiant energy can alsobe useful including, but not limited to, other wavelengths of light,other frequencies of ultrasound, x-rays, gamma-rays, microwave radiationand hypersound.

In the case of radiant light, the energy delivering element can includea light transmitting optical fiber adapted to receive ablative radiationfrom a radiation source and a light emitting tip at a distal end of thefiber for emitting radiation. The light delivering element can beslidably disposed within an inner lumen of the catheter body and theinstrument can further include a translatory mechanism for disposing thetip of the light delivering element at one or more of a plurality oflocations with the catheter. Moreover, by moving the energy-projectingtip assembly within the catheter, the diameter of the projected ring ofenergy can be readily varied, thereby permitting the clinician controlover the location (and size) of the lesion to be formed.

Optionally, a fluid can be disposable between the radiant energydelivery element and the target region. In one preferred embodiment a“projection balloon” is filled with a radiation-transmissive fluid sothat radiant energy from the energy emitter can be efficiently passedthrough the instrument to the target region. The fluid can also be usedto cool the energy emitter. In certain applications, it can be desirableto use deuterium oxide (so-called “heavy water”) as a balloon-fillingfluid medium because of its loss of absorption characteristics vis-à-visinfrared radiation. In other applications, the inflation fluid can bewater or saline.

It can also be desirable to employ an “ablative fluid” outside of theinstrument (e.g., between the balloon and the target region) to ensureefficient transmission of the radiant energy when the instrument isdeployed. An “ablative fluid” in this context is any fluid that canserve as a conductor of the radiant energy. This fluid can be aphysiologically compatible fluid, such as saline, or any other non-toxicaqueous fluid that is substantially transparent to the radiation. In onepreferred embodiment, the fluid is released via one or more exit portsin the housing and flows between the projection balloon and thesurrounding tissue, thereby filling any gaps where the balloon does notcontact the tissue. The fluid can also serve an irrigation function bydisplacing any blood within the path of the radiant energy, which couldotherwise interfere because of the highly absorptive nature of bloodwith respect to radiant light energy.

Similarly, if the radiant energy is acoustic, aqueous coupling fluidscan be used to ensure high transmission of the energy to the tissue (andlikewise displace blood that might interfere with the radiant acousticenergy transfer).

The ablative fluids of the present invention can also include variousother adjuvants, including, for example, photosensitizing agents,pharmacological agents, and/or analgesics.

As noted above, contact sensing mechanisms are also disclosed to assistthe clinician in selecting the location of the lesion and in ensuring aselected location will result in the formation of a continuous (e.g.,vein encircling) lesion. In one embodiment, the sensor employs aplurality of reflection sensors that indicate whether or not a cleartransmission pathway has been established (e.g., whether the projectionballoon is properly seated and any gaps in contact have been filled byan ablative fluid).

The coaxial catheter instruments disclosed herein are of particular usein percutaneous applications whereby a balloon catheter with an ablativelight or ultrasound projecting assembly can be disposed within apatient's heart. In another aspect of the invention, dual, coaxialballoon structures are disclosed, having both a projection balloon andan anchoring balloon to assist in the proper disposition of theinstrument.

In the dual, coaxial, catheter embodiment, the catheter instrument caninclude at least one expandable anchor balloon disposed about, orincorporated into, an inner catheter body designed to slide over aguidewire. This anchor balloon is generally or substantially sealed andserves to position the device within a lumen, such as a pulmonary vein.The anchor balloon structure, when filled with fluid, expands and isengaged in contact with tissue, e.g., the inner surface of a pulmonaryvein.

A second catheter carrying the projection balloon can then be slid overthe first (anchor balloon) catheter body and inflated within the heart,e.g., within the left atrium and adjacent to the pulmonary vein wherethe anchor balloon has already been placed. The expanded projectionballoon thus defines a staging from which to project radiant energy inaccordance with the invention. An energy emitting element can then beintroduced via an inner lumen to project radiant energy, e.g., infraredlight or ultrasound, through the coaxial catheter bodies and theprojection balloon to form a lesion at the target treatment site. Theinstrument can also include an irrigation mechanism for delivery of anablative fluid at the treatment site. In one embodiment, irrigation isprovided by a sheath, partially disposed about the projection balloon,and provides irrigation at a treatment site (e.g., so that blood can becleared from an ablation site).

Both the anchor and projection balloon structures can be deflated byapplying a vacuum which removes the fluid from the balloons. Once fullydeflated, the coaxial instrument can be removed from the body lumeneither as an ensemble, or as individual elements (starting with theinnermost element). Alternatively, the energy delivery element can beremoved (via an inner lumen balloon structure), followed by theprojection balloon catheter and then the anchor balloon catheter.

The invention can also be used in conjunction with one or more mappingcatheters. For example the guide wire element (and/or the anchorageballoon catheter) can be removed and replaced with a mapping catheterbefore and/or after the lesion is formed to determine whether theablation has been successful in stopping errant electrical signals frompropagating in the atrial wall tissue.

The present invention also provides methods for ablating tissue. Onemethod of ablating tissue comprises positioning a radiant energyemitting element at a distance from a target region of tissue, providinga blood-free transmission pathway between the emitter and the targetregion, and then projecting radiant energy to expose the target regionand induce a lesion.

In one method according to the invention, a guide wire can be insertedinto the femoral vein and advanced through the inferior vena cava, andinto the right atrium, or, if required, guided into the left atrium viaan atrial septal puncture. In either event, the guide wire can beadvanced until it enters a pulmonary vein. The first catheter body canthen be slid over the guide wire until its anchorage element, e.g., theanchor balloon, is likewise advanced into the pulmonary vein. The anchorballoon can then be inflated via an inflation fluid to secure the firstcatheter body. Next, a second catheter body can be advanced, coaxially,over the first catheter body, carrying a projection balloon to thetreatment site. Once the projection balloon is proximate to the targettissue ablation site, it can likewise be inflated. In addition, asolution can be injected through the instrument to force blood and/orbody fluids away from the treatment site.

The guide wire can then be removed and replaced with the radiant energyemitter, which is positioned to deliver radiant energy through theprojection balloon to induce tissue ablation. The methods of the presentinvention can further include a position sensing step to assist theclinician in selecting the location of the lesion and in ensuring aselected location will result in the formation of a continuous (e.g.,vein encircling) lesion. In one embodiment, one or more reflectionsensors can be activated to determine whether a clear transmissionpathway has been established (e.g., whether the projection balloon isproperly seated and any gaps in contact have been filled by an ablativefluid).

Following the ablation procedure, the radiant energy emitter can beremoved from the central lumen of the first catheter body. The anchorballoon can then be deflated by applying a vacuum that removes theinflation fluid from the balloon. A syringe or other known methods canbe used to remove the fluid. In one embodiment, the anchor balloon canbe deflated first and removed along with the first (inner) catheterbody. The first catheter body can then be replaced with a mappingcatheter. Once the mapping electrode is advanced into the pulmonaryvein, the projection balloon can be likewise deflated and the secondcatheter body removed, thus leaving only the mapping catheter in place.The mapping catheter can then be activated to determine whether aconduction block has been achieved. If the ablation is successful, themapping catheter can be removed. If conduction is still present, theprocedure can be repeated, for example, by reintroducing the secondcatheter body, followed by removal of the mapping catheter, andrepositioning the anchor balloon and the radiant energy emitter.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will be more fully understood from the following detaileddescription taken in conjunction with the accompanying drawings, inwhich like reference numerals designate like parts throughout thefigures, and wherein:

FIG. 1 is a schematic, cross-sectional view of a coaxial catheterablation instrument according to the invention;

FIG. 2 is a schematic illustration of an initial step in performingablative surgery with radiant energy according to the invention, inwhich a guide wire is introduced into a heart and passed into apulmonary vein;

FIG. 3 is a schematic illustration of another step in performingablative surgery with radiant energy according to the invention, inwhich a first catheter, carrying an anchoring balloon structure, is slidover the guide wire;

FIG. 4 is a schematic illustration of a further step in performingablative surgery according to the invention, in which an anchoringballoon structure is inflated;

FIG. 5 is a schematic illustration of a further step in performingablative surgery according to the invention, in which a second catheter,carrying a projection balloon element, is slid over the first catheterbody;

FIG. 6 is a schematic illustration of a further step in performingablative surgery according to the invention, in which the projectionballoon element of the second catheter is inflated to define aprojection pathway for radiant energy ablation of cardiac tissue;

FIG. 7 is a schematic illustration of a further step in performingablative surgery according to the invention, in which the guide wire isremoved and replaced by a radiant energy emitter located remote from thelesion site but in a position that permits projection of radiant energyonto a target region of the heart;

FIG. 8 is a schematic illustration of a step in performing ablativesurgery according to the invention, in which the radiant energy emitteris positioned to form a lesion at a defined location;

FIG. 9 is a schematic illustration of an alternative step in performingablative surgery according to the invention, in which the radiant energyemitter is positioned to form a lesion at a different defined location;

FIG. 10 is a schematic illustration of a further step in performingablative surgery according to the invention, in which the radiant energyemitter is removed and the anchor balloon element of the first catheteris deflated to permit removal of the first catheter body;

FIG. 11 is a schematic illustration of a further step in performingablative surgery according to the invention, in which the first catheteris replaced by a mapping electrode;

FIG. 12 is a schematic illustration of a further step in performingablative surgery according to the invention, in which the projectionballoon is deflated and removed while the mapping electrode remains inplace to verify the formation of an electrical conduction block;

FIG. 13 is a schematic illustration of an alternative approach toablative surgery with radiant energy according to the invention, inwhich a catheter carrying a projection balloon structure is slid over aguide wire without first introducing an anchoring balloon catheter;

FIG. 14 is a schematic illustration of a further step in performingablative surgery with the embodiment illustrated in FIG. 13, in whichthe projection balloon element is inflated to define a projectionpathway for radiant energy ablation of cardiac tissue;

FIG. 15 is a schematic illustration of a further step in performingablative surgery with the embodiment illustrated in FIG. 13, in whichthe guide wire is removed and replaced by a radiant energy emitterlocated remote from the lesion site but in a position that permitsprojection of radiant energy onto a target region of the heart;

FIG. 16 is a schematic illustration of a system according to theinvention in which an asymmetric vein mouth is encountered and furthershowing how the position of the radiant energy emitter can be adjustedto sense contact and select a location;

FIG. 16A illustrates how a continuous, vein-encircling lesion can beformed by two partially-encircling lesions;

FIG. 17 is a schematic illustration of one embodiment of a radiant lightenergy emitter according to the invention;

FIG. 18 is a schematic illustration of another embodiment of a radiantlight energy emitter according to the invention;

FIG. 19 is a schematic illustration of an alternative embodiment of aradiant energy emitter according to the invention employing ultrasoundenergy;

FIG. 20 is a schematic illustration of an alternative embodiment of aradiant light energy emitter according to the invention employingmicrowave or ionizing radiation;

FIG. 21 is a schematic cross-sectional illustration of one embodiment ofa contact sensor according to the invention;

FIG. 22 is an end view, schematic illustration of the contact sensorelements shown in FIG. 21;

FIG. 23 is a schematic view of a contact heating ablation deviceemploying the contacting sensing apparatus of the present invention;

FIG. 23A is a schematic view of a cryogenic ablation device employingthe contacting sensing apparatus of the present invention;

FIG. 23B is a schematic view of an ultrasound heating ablation deviceemploying the contacting sensing apparatus of the present invention; and

FIG. 24 is a schematic illustration of a mechanism for positioning theradiant energy emitter at a selected location relative to the targettissue region.

DETAILED DESCRIPTION

FIG. 1 provides a schematic, cross-sectional view of a coaxial catheterablation instrument 10 according to the invention, including a first,inner catheter 12 having an elongate body 14 and an anchor balloon 16inflatable via one or more ports 18. A fluid for inflating the anchorballoon can be delivered through a passageway (not shown) within theelongate body or via one or more of the lumens of the device, asdiscussed in more detail below. The device can further include a second,coaxial, outer catheter 20 having an elongate body 24 and a projectionballoon 26 inflatable via one or more ports 22. The instrument ispreferably designed such that upon anchorage of the anchor balloon 16within the heart (e.g., within a pulmonary vein), the projection ballooncan be inflated such that a shoulder portion 50 of the balloon 26 willbe urged into close proximity with a target region 52 of cardiac tissue(e.g. an annular region of the atrial heart wall surrounding the ostiumof a pulmonary vein).

The instrument can also include one or more ports 36 (in fluidcommunication with either the first catheter 12 or second catheter 20,or both) for delivering ablative fluid to the target region. Preferably,the ablative fluid is an energy transmissive medium, which helps deliverlight, radiation, or acoustic energy from a radiant energy source to atarget tissue region. The ablative fluid also serves to clear blood fromthe vicinity of the instrument and compensate for irregularities in theshape of the heart that might otherwise compromise the seating of theinstrument. The ablative fluid thus provides a clear transmissionpathway external to the balloon.

Within the projection balloon 26 a radiant energy emitter 40 can bedisposed remotely from the target tissue (e.g., within a central lumenof the coaxial catheters 12, 20). In one embodiment, the radiant energysource includes at least one optical fiber 42 coupled to a distal lightprojecting optical element 43, which cooperate to project ablative lightenergy through the instrument to the target site. The catheter bodies,projection balloon, and inflation/ablation fluids are all preferablysubstantially transparent to the radiant energy at the selectedwavelength to provide a low-loss transmission pathway from theprojection element 44 to the target.

FIG. 2 is a schematic illustration of an initial step in performingablative surgery with radiant energy according to the invention, inwhich a guide wire 6 is introduced into a heart 2 and passed into apulmonary vein 4. FIG. 3 illustrates the next step in performingablative surgery according to the invention, in which a first catheter12, carrying an anchoring balloon structure 16, is slid over the guidewire 6. This first catheter 12 can further include at least one internalfluid passageway (not shown) for inflation of the balloon 12, which issealed to the body of the catheter 14 by distal seal 15 and proximalseal 17, such that the introduction of an inflation fluid into theballoon 16 can inflate the balloon as shown in FIG. 4. For furtherdetails on anchoring balloon structures, see commonly owned U.S. patentapplication Ser. No. 09/616,303 filed Jul. 14, 2000 and now U.S. Pat.No. 6,796,972 issued on Sep. 28, 2004, entitled “Catheter AnchoringBalloon Structure with Irrigation,” the disclosures of which are herebyincorporated by reference.

FIG. 5 is a schematic illustration of a further step in performingablative surgery according to the invention, in which a second catheter20, likewise having a elongated body 24 and carrying a projectionballoon element 26, is slid over the first catheter body 14. This secondcatheter 20 also includes at least one internal fluid passageway (notshown) for inflation of the balloon 26, which is sealed to the body 24of the catheter 20 by distal seal 21 and proximal seal 22, such that theintroduction of an inflation fluid into the balloon 26 can inflate theballoon as shown in FIG. 6.

Thus, FIG. 6 illustrates how the projection balloon 26 of the secondcatheter 20 can be deployed and inflated to define a projection pathwayfor radiant energy ablation of cardiac tissue. Second catheter body 24has an inner lumen 27 sized to pass over the inner catheter body 14.Once it is positioned in the heart, the projection balloon of the secondcatheter is then inflated. The expanded projection balloon defines astaging through which radiant energy can be projected in accordance withthe invention. In one preferred embodiment, the projection balloon isfilled with a radiation-transmissive fluid so that radiant energy froman energy emitter can be efficiently passed through the instrument to atarget region of cardiac tissue.

The projection balloons described herein can be preshaped to form aparabolic like shape. This can be accomplished, for example, by shapingand melting a TEFLON® film in a preshaped mold to effect the desiredform. The projection balloons and sheaths of the present invention canbe made, for example, of thin wall polyethylene teraphthalate (PET) witha thickness of the membranes of about 5-50 micrometers.

It should be noted that it is not necessary (and in some cases, notdesirable) for the projection balloon 26 to contact the target tissue inorder to ensure radiant energy transmission. One purpose of theprojection balloon is simply to clear a volume of blood away from thepath of the energy emitter. With reference again to FIG. 1, an ablativefluid 29 can be employed outside of the instrument (e.g., between theballoon 26 and the target region 52) to ensure efficient transmission ofthe radiant energy when the instrument is deployed. The ablative fluidin this context is any fluid that can serve as a conductor of theradiant energy. This ablative fluid can be a physiologically compatiblefluid, such as saline, or any other non-toxic aqueous fluid that issubstantially transparent to the radiation. As shown in FIG. 1, thefluid 29 can be released via one or more exit ports 36 in the firstcatheter body 14 (and/or second catheter body 24) to flow between theprojection balloon 26 and the surrounding tissue, thereby filling anygaps where the balloon 26 does not contact the tissue. The fluid 29 canalso serve an irrigation function by displacing any blood within thepath of the radiant energy, which could otherwise interfere with theradiant light energy transmission to the target region 52.

For alternative designs for delivery of ablative and/or irrigationfluids, see commonly-owned, U.S. patent application Ser. No. 09/660,601,filed Sep. 13, 2000 and now U.S. Pat. No. 6,605,055 issued Aug. 12,2003, entitled “Balloon Catheter with Irrigation Sheath,” thedisclosures of which are hereby incorporated by reference. For example,in one embodiment described in patent application Ser. No. 09/660,601,the projection balloon can be partially surrounded by a sheath thatcontains pores for releasing fluid near or at the target ablation site.A person having ordinary skill in the art will readily appreciate thatsuch pores can vary in shape, size, and/or quantity, and that placementof the fluid ports of various designs can be varied to provide a desiredamount of fluid to the treatment site.

FIG. 7 is a schematic illustration of a further step in performingablative surgery according to the invention, in which the guide wire isremoved and replaced by a energy emitter 40 located remote from thedesired lesion site 52 but in a position that permits projection ofradiant energy onto a target region of the heart. The energy emitter canbe introduced into the instrument via the lumen 13 of the innercatheter. In the illustrated embodiment, the energy emitter 40 is aradiant energy emitter and includes at least one optical fiber 42coupled to a distal light projecting, optical element 43, whichcooperate to project ablative light energy through the instrument to thetarget site. In one preferred embodiment, optical element is a lenselement capable of projecting an annular (ring-shaped) beam ofradiation, as described in more detail in commonly owned U.S. Pat. No.6,423,055 issued Jul. 22, 2002, herein incorporated by reference.

FIGS. 8 and 9, taken together, illustrate an advantageous feature of thepresent invention, namely, the ability to select the location of alesion independent of the instrument design. Because the radiant energyemitter does not require contact with a target tissue region and is, infact, decoupled from the rest of the instrument, the present inventionpermits the clinician to select a desired target region by simply movingthe emitter (e.g., within the lumen 14 of the first catheter 12). Asshown in FIG. 8, the radiant energy emitter can be positioned to form awide circumferential lesion (when the shape of the pulmonary vein ostiumwarrants such a lesion) by positioning the radiant energy emitter at therear of the projection balloon—at a distance from the target tissue.Alternatively, a smaller diameter lesion can be formed by positioningthe radiant energy emitter closer to the front of the projectionballoon, as shown in FIG. 9. Such a lesion can be preferable when thegeometry of the vein ostium presents a more gradual change in diameter,as shown. It should be appreciated that it may be desirable to changethe intensity of the emitted radiation depending upon the distance itmust be projected; thus a more intense radiant energy beam may bedesirable in the scheme illustrated in FIG. 8 versus that shown in FIG.9. The energy emitter 40 and catheter body 24 can each include one ormore markers (shown schematically as elements 33 and 35, respectively)to aid in determining the location or tracking movements of theelements. Markers 33 and 35, for example, can be radiopaque lines thatcan be visualized fluoroscopically. Various other marker mechanisms,such as magnetic, capacitive, or optical markers, can also be used.

FIG. 10 is a schematic illustration of a further step in performingablative surgery according to the invention, in which the radiant energyemitter 40 (shown in FIGS. 7-9) has been removed and the anchor balloonelement 16 of the first catheter 12 is deflated to permit removal of thefirst catheter body 14.

In FIG. 11, the first catheter is replaced by a mapping electrodecatheter 88 via, for example, the central lumen of the second catheter20. However, it should be appreciated that more than one lumen can beused to provide separate pathways for these instruments. Once themapping electrode is positioned within a pulmonary vein, an electricalpulse can be applied to determine whether the lesion formed by theradiant energy emitter (as described above) is sufficient to serve as aconduction block.

FIG. 12 is a schematic illustration of a final step in which theprojection balloon is deflated and removed while the mapping electroderemains in place to verify the formation of an electrical conductionblock. Various techniques for conducting such tests are known by thoseskilled in the art. In one simple approach, a voltage pulse is appliedby a coronary sinus catheter. The mapping catheter's electrode istouched to the inner wall of the pulmonary vein. If no signal (or asubstantially attenuated signal) is detected, a conduction block canthereby be confirmed. It should also be appreciated that the mappingelectrode can in some instances be used even before the projectionand/or anchor balloons are removed.

FIG. 13 is a schematic illustration of an alternative method ofperforming ablative surgery with radiant energy according to theinvention without the need for an anchoring balloon. As shown in FIG.13, a guide wire 6 can again be introduced into a heart and passed intoa pulmonary vein 4. A catheter 20 carrying projection balloon structure26 is slid over the guide wire 6. This catheter 20 can further includeat least one internal fluid passageway (not shown) for inflation of theballoon 26, which is sealed to the body of the catheter 20 by distalseal 21 and proximal seal 22, such that the introduction of an inflationfluid into the balloon 26 can inflate the balloon.

FIG. 14 illustrates how the projection balloon 26 can then be inflatedto define a projection pathway for radiant energy ablation of cardiactissue. The expanded projection balloon defines a staging through whichradiant energy can be projected in accordance with the invention. In onepreferred embodiment, the projection balloon is filled with aradiation-transmissive fluid so that radiant energy from an energyemitter can be efficiently passed through the instrument to a targetregion of cardiac tissue.

The projection balloons described herein can be preshaped to formvarious shapes (e.g., to assist in seating the instrument at the mouthof a pulmonary vein or at other anatomically defined regions of theheart). As noted above, this can be accomplished, for example, byshaping and melting a TEFLON® film in a preshaped mold to effect thedesired form. Again, the projection balloons can be made, for example,of thin wall polyethylene teraphthalate (PET) with a thickness of themembranes of about 5-50 micrometers.

One purpose of the projection balloon is to clear a volume of blood awayfrom the path of the energy emitter. Towards this end, the instrumentcan further include a fluid releasing mechanism in the form of one ormore fluid ports (or a sheath that contains pores for releasing fluid)near or at the target ablation site. Again, the released fluid can serveas an ablative fluid by clearing a transmission pathway for radiantenergy.

FIG. 15 is a schematic illustration of a further step in performingablative surgery with the device of FIGS. 13-14, in which the guide wireis removed and replaced by a radiant energy emitter 40 located remotefrom the desired lesion site 52 but in a position that permitsprojection of radiant energy onto a target region of the heart. In theillustrated embodiment, the radiant energy emitter 40 includes at leastone optical fiber 42 coupled to a distal light projecting, opticalelement 43, which cooperate to project ablative light energy through theinstrument to the target site. In one preferred embodiment, the opticalelement is again a lens element capable of projecting an annular(ring-shaped) beam of radiation, as described in more detail in commonlyowned U.S. Pat. No. 6,423,055 issued Jul. 22, 2002, herein incorporatedby reference. Alternatively, the radiant energy emitter can be anultrasound or microwave energy source, as described in more detail below(in connection with FIGS. 19-20).

FIG. 16 further illustrates the unique utility of themulti-positionable, radiant energy ablation devices of the presentinvention in treating the complex cardiac geometries that are oftenencountered. As shown in the figure, the mouths of pulmonary veinstypically do not present simple, funnel-shaped, or regular conicalsurfaces. Instead, one side of the ostium 4B can present a gentlesloping surface, while another side 4A presents a sharper bend. Withprior art, contact-heating, ablation devices, such geometries willresult in incomplete lesions if the heating element (typically aresisting heating band on the surface of an expandable element) can notfully engage the tissue of the vein or ostium. Because the position ofthe heating band of the prior art devices is fixed, when it does notfully contact the target tissue, the result is an arc, or anincompletely formed ring-type, lesion that typically will beinsufficient to block conduction.

FIG. 16 illustrates how the slidably positionable energy emitters of thepresent invention can be used to avoid this problem. Three potentialpositions of the emitter 40 are shown in the figure (labeled as “A”, “B”and “C”). As shown, positions A and C may not result in optimal lesionsbecause of gaps between the balloon and the target tissue. Position B,on the other hand, is preferable because circumferential contact hasbeen achieved. Thus, the independent positioning of the energy sourcerelative to the balloon allows the clinician to “dial” an appropriatelyring size to meet the encountered geometry. (Although three discretelocations are shown in FIG. 16, it should be clear that emitter can bepositioned in many more positions and that the location can be varied ineither discrete intervals or continuously, if so desired.)

Moreover, in some instances the geometries of the pulmonary vein (or theorientation of the projection balloon relative to the ostium) may besuch that no single annular lesion can form a continuous conductionblock. Again, the present invention provides a mechanism for addressingthis problem by adjustment of the location of the energy emitter to formtwo or more partially circumferential lesions. As shown in FIG. 16A, thedevices of the present invention can form a first lesion 94 and a secondlesion 96, each in the form of an arc or partial ring. Because eachlesion has a thickness (dependent largely by the amount of energydeposited into the tissue) the two lesions can axially combine, asshown, to form a continuous encircling or circumscribing lesion thatblocks conduction.

FIG. 17 is a schematic illustration of one embodiment of a radiantenergy emitter 40A according to the invention. In one preferredembodiment, the radiant energy is electromagnetic radiation, e.g.,coherent or laser light, and the energy emitter 40A projects a hollowcone of radiation that forms an annular exposure pattern uponimpingement with a target surface. For example, as shown in FIG. 17, theradiant energy emitter 40A can include an optical fiber 42 incommunication with an annulus-forming optical waveguide 44 having aconcave interior boundary or surface 45. The waveguide 44 passes anannular beam of light to a graded intensity (GRIN) lens 46, which servesto collimate the beam, keeping the beam width the same, over theprojected distance. The beam that exits from the distal window 48 ofenergy emitter 40A will expand (in diameter) over distance, but theenergy will remain largely confined to a narrow annular band. Generally,the angle of projection from the central axis of the optical fiber 42 orwaveguide 44 will be between about 20 and 45 degrees.

The diameter of the annular beam of light will be dependent upon thedistance from the point of projection to point of capture by a surface,e.g., a tissue site, e.g., an interstitial cavity or lumen. Typically,when the purpose of the radiant energy projection is to form atransmutably cardiac lesion, e.g., around a pulmonary vein, the diameterof the annular beam will be between about 10 mm and 33 mm, preferablygreater than about 10 mm, greater than about 15 mm, greater than about20 mm, and most preferably, greater than or equal to about 23 mm.Typically, the angle of projected annular light is between about 20 and45 degrees, preferably between about 17 and 30 degrees, and mostpreferably between about 16 and 25 degrees.

Preferred energy sources for use with the percutaneous ablationinstruments of the present invention include laser light in the rangebetween about 200 nanometers and 2.5 micrometers. In particular,wavelengths that correspond to, or are near, water absorption peaks areoften preferred. Such wavelengths include those between about 805 nm and1060 nm, preferably between about 900 nm and 1000 nm, and mostpreferably, between about 915 nm and 980 nm. In a preferred embodiment,wavelengths around 915 nm or around 980 nm are used during endocardialprocedures. Suitable lasers include excimer lasers, gas lasers, solidstate lasers and laser diodes. One preferred AlGaAs diode array,manufactured by Spectra Physics, Tucson, Ariz., produces a wavelength of980 nm.

The optical waveguides, as described in above, can be made frommaterials known in the art such as quartz, fused silica, or polymerssuch as acrylics. Suitable examples of acrylics include acrylates,polyacrylic acid (PAA) and methacrylates, polymethacrylic acid (PMA).Representative examples of polyacrylic esters include polymethylacrylate(PMA), polyethylacrylate and polypropylacrylate. Representative examplesof polymethacrylic esters include polymethylmethacrylate (PMMA),polyethylmethacrylate and polypropylmethacrylate. In one preferredembodiment, the waveguide 44 is formed of quartz and fused to the endface of fiber 42.

Internal shaping of the waveguide can be accomplished by removing aportion of material from a unitary body, e.g., a cylinder or rod.Methods known in the art can be utilized to modify the waveguide to havetapered inner walls, e.g., by grinding, milling, ablating, etc. In oneapproach, a hollow polymeric cylinder, e.g., a tube, is heated so thatthe proximal end collapses and fuses together, forming an integralproximal portion which tapers to the distal end of the waveguide. Inanother approach, the conical surface 45 can be formed in a solid quartzcylinder or rod by drilling with a tapered bore.

The waveguide 44 can be optically coupled to optical fiber 42 by variousmethods known in the art. These methods include for example, gluing, orfusing with a torch or carbon dioxide laser. In one embodiment (shown inFIG. 19), waveguide 44, optical fiber 42 and, optionally, a gradientindex lens (GRIN) 46 are in communication and are held in position byheat shrinking a polymeric jacket material 49, such as polyethyleneterephthalate (PET) about the optical apparatus.

FIG. 18 is a schematic illustration of another embodiment of a radiantenergy emitter 40B according to the invention in which optical fiber 42is coupled to a light diffuser 41 having light scattering particles 47to produce a sidewise cylindrical exposure pattern of ablativeradiation. This embodiment can be useful, for example, in creating alesion within a pulmonary vein. With reference again to FIG. 1, itshould be clear that the radiant energy emitter of the design shown inFIG. 14 can be advanced to the front of the projection balloon to permitdiffuse exposure of a pulmonary vein ostium if a lesion is desired inthat location. For further details on the construction of lightdiffusing elements, see U.S. Pat. No. 5,908,415 issued to Sinofsky onJun. 1, 1999, herein incorporated by reference.

FIG. 19 illustrates an alternative embodiment of a radiant energyemitter 40C in which an ultrasound transducer 60 comprises individualshaped transducer elements or lenses 62, which direct the ultrasoundenergy into a cone of energy that can likewise form an annular exposurepattern upon impingement with a target surface. The emitter 40C issupported by a sheath 66 or similar elongate body, enclosing electricalleads, and thereby permitting the clinician to advance the emitterthrough an inner lumen of the instrument to a desired position forultrasound emission.

Yet another embodiment of a radiant energy emitter 40D is illustrated inFIG. 20 where microwave energy is similarly focused into an annularexposure beam. As shown in FIG. 20, the radiant energy emitter caninclude a coaxial transmission line 74 (or similar electrical signalleads) and a helical coil antenna 73. Radiation reflectors 72A and 72Bcooperate to shield and direct the radiation into a cone. In otherembodiments, a radioisotope or other source of ionizing radiation can beused in lieu of the microwave antenna 73, again with appropriateradiation shielding elements 72A and 72B to project a beam of ionizingradiation.

FIGS. 21 and 22 illustrate one embodiment of a contact sensor accordingto the invention incorporated into a radiant emitter assembly. Theassembly can include an outer, radiant energy transparent body 70 thatencases the assembly and facilitates its slidable positioning within aninner lumen of catheter body 14. The assembly further includes an energyemitter 40 (e.g., like those described above in connection with FIGS.17-20) which can also act as the sensing fiber. In the illustratedembodiment, four illumination fibers 76A-76D are shown. If the ablativeapparatus of the invention is properly positioned within the heart,light transmitted via such fibers will strike the target region, bereflected back, and be detected by the energy emitter (or other sensingelement). The use of four illumination fibers allows simultaneous orsequential sensing of contact in four “quadrants.” It should be clearthat the invention can be practiced with various numbers of illuminatingand/or sensing elements, and with or without use of the energy emitteras an element in the contact sensing module. Moreover, ultrasoundemitters and detectors can also be used in the same manner in lieu ofthe light reflecting mechanisms to determine contact. In any event, theoutput signals of the sensors can be electronically processed andincorporated into a display.

The sensors of FIGS. 21-22 provide the ability to position thepercutaneous ablation instruments of the present invention at atreatment site such that proper location of the energy emitter vis-à-visthe target tissue (as well a satisfactory degree of contact between theprojection balloon and the tissue) is achieved. This ability is based onreflectance measurements of light scattered or absorbed by blood, bodyfluids, and tissue. For example, white light projected from sensingfibers 76 toward tissue has several components including red and greenlight. Red light has a wavelength range of about 600 to about 700nanometers (nm) and green light has a wavelength range of about 500 toabout 600 nm. When the projected light encounters blood or body fluids,most if not all green light is absorbed and hence very little green orblue light will be reflected back toward the optical assembly whichincludes a reflected light collector. As the apparatus is positionedsuch that blood and body fluids are removed from the treatment fieldcleared by an inflated balloon member, the reflectance of green and bluelight increases as biological tissue tends to reflect more green light.As a consequence, the amount of reflected green or blue light determineswhether there is blood between the apparatus and the tissue.

For example, as the instrument is positioned in a heart chamber, thegreen-blue reflectance signal should remain nearly at zero until theprojection balloon is inflated and positioned proximal to the surface ofthe heart tissue. When the inflated balloon member contacts the hearttissue (or is close enough that the balloon and ablative fluid releasedby the instrument form a clear transmission pathway), green light isreflected back into the optical assembly and the collector. In oneembodiment, only green light is projected toward the tissue surface. Inanother embodiment, red and green light are both projected toward thetissue surface. The red and green light can be transmittedsimultaneously or separately. The use of both red and green lightprovides the advantage that there is no requirement that the operatorneeds to know how much light must be transmitted into the balloon towardthe tissue surface to insure that a reflectance signal is returned. Theratio of the two different wavelengths can be measured. For example, theinstrument can measure reflectance of both green light and red light.When the intensity of the light is sufficient, reflected red light isdetected throughout the positioning process. Prior to contact of theinstrument, and more specifically the inflated balloon, with the tissue,the ratio of red light to green light would be high. Once a transmissionpathway is established, the ratio drops since more light is reflectedfrom the tissue without any intervening blood to absorb the green light.

The reflected light is transmitted back through a collector, such as anoptical fiber to a spectrophotometer. The spectrophotometer (OceanOptics Spectrometer, Dunedin, Florida, model S-2000) produces a spectrumfor each reflected pulse of reflected light. Commercially availablesoftware (LabView Software, Austin, Tex.) can isolate values forspecific colors and perform ratio analyses.

In any event, the use of multiple optical fiber illumination fiberspositioned about the lumen of the catheter permit the operator todetermine the plane in which the catheter and balloon should be adjustedto minimize blood between the optical assembly and the treatment site.One suitable optical fiber/collector is described in U.S. Pat. No.6,071,302, issued to Edward Sinofsky on Jun. 6, 2000, the contents ofwhich are incorporated herein by reference.

Once the operator is satisfied with the positioning of the instrument,radiant energy can then be projected to the target tissue region. If theradiant energy is electromagnetic radiation, e.g., laser radiation, itcan be emitted onto the tissue site via a separate optical fiber or,alternatively, through the same optical fiber used to transmit thewhite, green or red light. The laser light can be pulsed intermittentlyin synchronous fashion with the positioning/reflecting light to ensurethat the pathway remains clear throughout the procedure.

It should be clear that the contact sensing aspects of the presentinvention are not limited to radiant energy ablation devices but canalso be useful in placement of contact heating or cooling ablationinstruments as well. For example, in FIG. 23, a contact-heating device54 having an expandable element 56 and a contact heating element 58 isshown disposed in a pulmonary vein. The contact heating element can be aline or grid of electrically conductive material printed on the surfaceof the expandable element. In one embodiment, the expandable element canbe substantially opaque to certain wavelengths (e.g., visible light)except for a transparent band 59, on which the contact heating elementis situated. The heating wires should also be sufficiently transparent(or cover a substantially small area of the band) so as to not interferewith reflection signal collection. The device 54 can further include asensor 76 disposed within a central lumen of the device having anilluminating fiber and a plurality of collecting fibers. The sensor 76can be coupled to an optical detector and analyzer 53 that is locatedexternal to the device and can be used to measure light received by thesensor and determine whether contact with the target tissue has beenachieved, as will be discussed in more detail below.

The contact sensor can operate in substantially the same fashion asdescribed above. For example, when the ablation device 54 of FIG. 23 ispositioned in a pulmonary vein, and illuminated with light from within,a green-blue reflectance signal should remain nearly at zero until theexpandable element 56 is inflated and positioned proximal to the surfaceof the heart tissue. When the portion of inflated expandable element 56that carries the ablation band 58 contacts the heart tissue, green lightis reflected back into the optical assembly and the collector. In oneembodiment, only green light is projected toward the tissue surface. Inanother embodiment, red and green light are both projected toward thetissue surface. The red and green light can be transmittedsimultaneously or separately. Again, the use of both red and green lightprovides the advantage that there is no requirement that the operatorneeds to know how much light must be transmitted into the balloon towardthe tissue surface to insure that a reflectance signal is returned. Theratio of the two different wavelengths can be measured by the opticaldetector and analyzer 53. For example, the instrument can measure thereflectance of both green light and red light. When the intensity of thelight is sufficient, reflected red light is detected throughout thepositioning process. Prior to contact of the instrument, and morespecifically the contact-heating ablation band, with the tissue, theratio of red light to green light would be high. Once contact isestablished, the ratio drops since more light is reflected from thetissue without any intervening blood to absorb the green light, andenergy can be delivered to the target tissue from, for example, aradio-frequency electric current source 55.

In FIG. 23A, another embodiment of a contact sensing catheter is shownin the form of a cryogenic ablation catheter 110 having a catheter body112 and internal conduits 114 for circulation of a cryogenic fluid froma cryogenic fluid source 115. The catheter body includes conductiveregions 116 where the cold temperature can be applied to tissue. Thesensors 76 of the present invention can be disposed in proximity to theconductive regions, as shown and used to determine whether tissuecontact has been made. For example, and similar to as discussed abovewith respect to FIG. 23, the sensors 76 can be coupled to an opticalanalyzer 53.

In FIG. 23B yet another application for the contact sensors is shown inconnection with an ultrasound, contact-heating balloon catheter 120having a balloon 122 (similar to that discussed above in connection withFIG. 23) for contacting a pulmonary vein and a band 123 for applyingheat to tissue. The ultrasound ablation instrument 120 further includestransducers 124 driven by an actuator 125 to heat the ablative band 123.Again, the sensors 76 of the present invention can be disposed inproximity to the ablation band 123, as shown, and used to determinewhether tissue contact has been made. For example, and similar to asdiscussed above with respect to FIG. 23, the sensors 76 can be coupledto an optical analyzer 53.

In FIG. 24, a translatory mechanism 80 is shown for controlled movementof a radiant energy emitter within the instruments of the presentinvention. The exemplary positioner 80 is incorporated into a handle 84in the proximal region of the instrument, where the elongate body 82 ofthe radiant energy emitter 40 engages a thumb wheel 86 to controladvancement and retraction of the emitter. It should be clear thatvarious alternative mechanisms of manual or automated nature can besubstituted for the illustrated thumb wheel 86 to position the emitterat a desired location relative to the target tissue region.

In addition, as shown in FIG. 24, the elongate body 82 that supports theradiant energy emitter 40 (e.g., an optical fiber assembly as shown inFIGS. 21-22 or the sheath for the electrical leads as shown inconnection with FIGS. 19-20) can further include position indicia 92 onits surface to assist the clinician in placement of the emitter withinthe projection balloon. The handle can further include a window 90whereby the user can read the indicia (e.g., gradation markers) to gaugehow far the emitter has been advanced into the instrument.

Although described in connection with cardiac ablation procedures, itshould be clear that the instruments of the present invention can beused for a variety of other procedures where treatment with radiantenergy is desirable, including laparoscopic, endoluminal, perivisceral,endoscopic, thoracoscopic, intra-articular, and hybrid approaches.

The term “radiant energy” as used herein is intended to encompass energysources that do not rely primarily on conductive or convective heattransfer. Such sources include, but are not limited to, acoustic andelectromagnetic radiation sources and, more specifically, includemicrowave, x-ray, gamma-ray, and radiant light sources. The term “light”as used herein is intended to encompass electromagnetic radiationincluding, but not limited to, visible light, infrared, and ultravioletradiation.

The term “continuous” in the context of a lesion is intended to mean alesion that substantially blocks electrical conduction between tissuesegments on opposite sides of the lesion. The terms “circumferential”and /or “curvilinear,” including derivatives thereof, are hereinintended to mean a path or line which forms an outer border or perimeterthat either partially or completely surrounds a region of tissue, orseparate one region of tissue from another. Further, a “circumferential”path or element may include one or more of several shapes, and may befor example, circular, annular, oblong, ovular, elliptical, or toroidal.

The term “lumen,” including derivatives thereof, in the context ofbiological structures, is herein intended to mean any cavity or lumenwithin the body which is defined at least in part by a tissue wall. Forexample, cardiac chambers, the uterus, the regions of thegastrointestinal tract, the urinary tract, and the arterial or venousvessels are all considered illustrative examples of body spaces withinthe intended meaning.

The term “catheter” as used herein is intended to encompass any hollowinstrument capable of penetrating body tissue or interstitial cavitiesand providing a conduit for selectively injecting a solution or gas,including without limitation, venous and arterial conduits of varioussizes and shapes, bronchoscopes, endoscopes, cystoscopes, culpascopes,colonscopes, trocars, laparoscopes, and the like. Catheters of thepresent invention can be constructed with biocompatible materials knownto those skilled in the art such as those listed supra, e.g., silastic,polyethylene, Teflon, polyurethanes, etc. The term “lumen,” includingderivatives thereof, in the context of catheters is intended toencompass any passageway within a catheter instrument (and/or trackotherwise joined to such instrument that can serve as a passageway) forthe passage of other component instruments or fluids or for delivery oftherapeutic agents or for sampling or otherwise detecting a condition ata remote region of the instrument.

It should be understood that the term “balloon” encompasses deformablehollow shapes which can be inflated into various configurationsincluding balloon, circular, tear drop, etc., shapes dependent upon therequirements of the body cavity. Such balloon elements can be elastic orsimply capable of unfolding or unwrapping into an expanded state.

The term “transparent” is well recognized in the art and is intended toinclude those materials which allow transmission of energy through, forexample, the primary balloon member. Preferred transparent materials donot significantly impede (e.g., result in losses of over 20 percent ofenergy transmitted) the energy being transferred from an energy emitterto the tissue or cell site. Suitable transparent materials includefluoropolymers, for example, fluorinated ethylene propylene (FEP),perfluoroalkoxy resin (PFA), polytetrafluoroethylene (PTFE), andethylene-tetrafluoroethylene (ETFE).

One skilled in the art will appreciate further features and advantagesof the invention based on the above-described embodiments. Accordingly,the invention is not to be limited by what has been particularly shownand described, except as indicated by the appended claims. Allpublications and references cited herein are expressly incorporatedherein by reference in their entirety.

1. A method of treating atrial fibrillation, comprising: seating adistal portion of a cardiac ablation instrument against tissue at alocation within a patient's heart adjacent an ostium of a pulmonaryvein, the instrument having a catheter body with at least one lumentherein and an energy emitting element independently positionable alonga longitudinal axis within the at least one lumen of the catheter body,wherein the instrument further includes an inflatable projection balloonthat surrounds the energy emitting element and defines the distalportion that is seated at the target location, the instrument having awave guide disposed at the distal end of the energy emitting element;positioning the energy emitting element at a first position relative tothe catheter body moving the energy emitting element along thelongitudinal axis to a first location; activating the energy emittingelement to project ablative energy to form a first partiallycircumferential lesion in a proximity of the ostium of the pulmonaryvein, the energy emitting element and projection balloon beingconstructed such that ablative energy is projected from the energyemitting element directly to a transmissive region of the projectionballoon that is in contact the tissue at the target location and permitsthe ablative energy to pass therethrough, the ablative energy contactingthe projection balloon in the transmissive region thereof; repositioningthe energy emitting element at a second position relative to thecatheter body by moving the energy emitting element along thelongitudinal axis to a second location, the distal portion of theinstrument remaining seated at said location; activating the energyemitting element to project ablative energy to form at least a secondpartially circumferential lesion in the proximity of the ostium of thepulmonary vein by projecting the ablative energy from the energyemitting element through the wave guide in a distal direction and at anacute angle relative to the longitudinal axis to the transmissive regionof the projection balloon that permits passage of the ablative energytherethrough, the ablative energy contacting the projection balloon inthe transmissive region thereof, the second partially circumferentiallesion being axially combined with the first partially circumferentiallesion and overlapping the first partially circumferential lesion atleast one location, the distal portion of the instrument remainingseated at said location; and continuing the steps of repositioning theenergy emitter along the longitudinal axis and activating until anaxially combined lesion is formed that encircles the pulmonary vein. 2.The method of claim 1, wherein each lesion is in the shape of an arc. 3.The method of claim 1, wherein each lesion has a similar thickness. 4.The method of claim 1, further comprising adjusting the position of theenergy emitting element such that the at least second lesion has adifferent thickness than the first lesion.
 5. The method of claim 1,further comprising inflating a projection balloon to clear blood from atransmission pathway between the energy emitting element and a targetregion of cardiac tissue.
 6. The method of claim 5, further comprisingdetermining whether a clear transmission path exists between the energyemitting element and the target region based on reflectance measurementsby an optical sensor disposed within the ablation instrument.
 7. Themethod of claim 6, further comprising measuring at least two differentwavelengths of reflected light collected by the optical sensor todetermine whether a projection path has been established.
 8. The methodof claim 1, wherein the step of activating the energy emitting elementfurther comprises activating a beam-forming optical waveguide to exposethe target region to an annular beam of light energy to induce thecombined lesion in cardiac tissue.
 9. The method of claim 1, wherein thestep of activating the energy emitting element further comprisesactivating a light emitting element to expose the target region to lightenergy to induce photocoagulation of cardiac tissue within the targetregion.
 10. The method of claim 1, wherein the step of activating theenergy emitting element further comprises activating a light emittingelement to expose the target region to light energy to induce thecombined lesion in the cardiac tissue.
 11. The method of claim 1,wherein the step of activating the energy emitting element furthercomprises generating photoablative radiation at a wavelength in therange of about 800 nm to 1000 nm.
 12. The method of claim 1, wherein thestep of activating the energy emitting element further comprisesgenerating photoablative radiation at a wavelength in the range of about915 nm to 980 nm.